There are many situations where containers having sludge-like mixtures must be cleaned by removing the solids fraction therefrom. Examples of such containers are septic tanks Septic tanks are generally cleaned using vacuum systems mounted on vehicles such as trucks. These vehicles can transport the vacuum systems were they are needed and then transport the removed waste content to appropriate waste disposal facilities or storage locations.
When cleaning a septic tank, it is generally desirable to return the liquid fraction back into the septic tank before the vehicle leaves the site. The liquid fraction contains micro-organisms promoting the decay of organic matters coming with the waste water into the septic tank. This way, the microflora then remains present inside the septic tank. Returning the liquid fraction also increases the number of sites a same vehicle can clean in a single run before emptying the accumulated waste content.
An example of a vehicle-mounted vacuum system is shown in U.S. Pat. No. 6,790,368 issued 14 Sep. 2004 to Vachon et al. Many other kinds of vacuum systems exist.
Typically, a conventional vacuum system first removes the entire content of a septic tank to be cleaned and transfers this content into one or more tanks on the vehicle. The solids and liquid fractions are separated onto the vehicle and the liquid matter is then returned back into the septic tank. This procedure, however, requires a relatively complex and costly dewatering arrangement on each vehicle. The internal components of the dewatering arrangement will not be available to the operator during the cleaning procedure and also until the tank or tanks on the vehicle are emptied, for instance at the waste disposal facility. Moreover, the intense intermixing of the content resulting from the integral vacuum pumping of the sludge-like mixture also makes the solids and liquid fractions even more difficult to separate. This dewatering procedure is thus not optimum. It also leaves a relatively a high proportion of liquids within the remaining waste content to be transported by the vehicle when it leaves the site.
Accordingly, there is still room for many improvements in this area of technology.